We're on a collision course with the Andromeda Galaxy — here's what will happen to Earth

An epic war is coming between our home galaxy and the Andromeda Galaxy, which is currently racing toward us at a speed of 250,000 mph.

Astronomers estimate that 3.75 billion years from now, Earth will be caught up amid the largest galactic event in our planet's history, when these two giant galaxies collide.

Luckily, experts think that Earth will survive, but it won't be entirely unaffected. The collision will unfold right in front of us, changing the night sky to look like nothing any human has seen before.

Far from city lights, on a clear night, this is what the sky on Earth looks like today. During certain times of the year, you can see the Andromeda Galaxy, circled below, next to the bright band of our own Milky Way.

Right now, Andromeda is about 2.5 million light-years away. When it collides with our galaxy in less than 4 billion years, it will enter into a cataclysmic dance lasting billions of years that will rip it and the Milky Way apart to form a new galaxy.

The two galaxies will make quick work of one another. Just 250 million years after the collision, the remains will be a ghostly skeleton of what was once two independent galaxies.

But it's not over. The battle will continue for billions of years until the supermassive black holes at the center of each galaxy get close enough to merge.

After 6 billion years of cosmic carnage, Earth's night sky will be ablaze with the elliptical galaxy's bright new core — that is, if Earth still exists, which isn't likely since the sun is expected to swallow it in about 5 billion years.

Because it takes billions of years for galaxies to fully merge, astronomers search the skies for different stages of the epic battle. Below is an example of two spiral galaxies in an early stage of merging, photographed by Hubble in 2009.